The present invention relates to an internal combustion engine suitable both for powering a vehicle and for research and development directed toward reduction of fuel consumption, reduction of pollutants and improvement of performance. The approach to these objectives is by way of a construction which makes it possible to control the timing and the overlap of both the intake and exhaust valves. Adjustment of these variables can be effected during operation of the engine either manually or automatically, using a detecting device for monitoring the performance of the engine, particularly with respect to fuel consumption and the amount of nitrogen oxides contained in the exhaust gases. A feature of substantial advantage is that the reduction in speed between crank shaft and cam shaft is effected by the same apparatus which provides for control of the valve timing and that both the reduction in speed and control of the valve timing are carried out with minimal power loss through friction.
In prior art internal combustion engines it has been the practice to drive the cam shaft by way of a gear formed integrally with the crank shaft, power being transmitted to the cam shaft either through a drive chain or another gear, and it has been impossible to change the rotational phase of the cam shaft with respect to the crank shaft. In view of the fact that the quantity of detrimental components in the exhaust gases and the fuel consumption of the engine depend upon the valve timing and upon the valve overlap, demands have recently arisen for an engine in which these functions could be varied. In a course of studies directed toward the development of an internal combustion engine in which the quantity of pollutants in the exhaust gases and in which the fuel consumption could be reduced, the present inventors have found that both fuel consumption and the quantity of nitrogen oxides in the exhaust gases could be reduced by changing the rotational phase of a cam shaft relative to the crank shaft in accordance with the load exerted on the engine.
As a result of this finding, it has been earnestly desired to provide an internal combustion engine which could provide for precise and easy control of the aforenoted variables and which, in addition, could easily be modified for investigation of the effect of combustion chamber configuration, type of valve-operating mechanism, modification of cam shape and number of cam shafts. Also, it should be possible to determine frictional loss, effects of operating temperature, special lubrication and any other pertinent factors which might be discovered.
There has been, as yet, no internal combustion engine which is really satisfactory for testing use, that is, for research and development. For instance, a change in the contour or type of combustion chamber may lead to requirement for a change in the positioning of valves or a change in the inclination of the valves, thus requiring a change in the positioning or contour of a cam shaft for operating either the intake valves or exhaust valves as well as remodeling of the driving portions for the respective valves. However, in conventional test engine constructions, interchange of cylinder heads to provide for a difference in contour and type of combustion chamber and positioning of valves is relatively difficult, making it impractical to carry out such tests so that the effect of such variables on performance cannot readily be determined. Moreover, where a serious attempt is made to carry out such tests, the resulting construction must be complex and the engine itself must be of substantially increased size, further increasing the difficulty of disassembling and reassembling the engine for each test. As is evident then, there has been a substantial need for an internal combustion engine which can serve as a practical device for powering a vehicle as well as other devices and which can also serve as a major piece of test equipment for research and development on the effect of intake and exhaust valve timing as well as other factors on fuel consumption, production of pollutants and general performance of internal combustion engines.